Various magnetic storage systems such as hard disk drives utilize a write head to record data on a magnetic medium. Data to be recorded is provided to the write head as an alternating electrical current. The electrical current passes through a metallic coil in the write head, generating a magnetic field. The magnetization state of a pole tip in the write head is switched by the magnetic field. As the magnetized pole tip is passed over the magnetic medium, for example a spinning disc having a ferromagnetic plating, the magnetization of regions of the magnetic medium adjacent the pole tip is altered and can later be read back to retrieve the data.
High density magnetic recording implies small grain size with its increased susceptibility to decay of fine-grained recorded information under thermal agitation. Thus, as the grain size is reduced to increase recording density, stability of the recorded information is also reduced. Increasing the ferromagnetic anisotropy of the recording medium reduces susceptibility to thermally-induced decay, but requires write fields in excess of those attainable with conventional write heads. One solution to the writeability versus longevity dilemma for magnetic storage systems is Heat Assisted Magnetic Recording (HAMR), which heats the magnetic medium in the vicinity of a written data bit to near the Curie point using a laser, allowing the write head to switch the magnetic orientation on the medium to store the data bit. Thus, a medium with greater thermal stability may be used with the limited write head field strength by spot-heating the magnetic medium as data are recorded.
There exists a need in the art for improving the laser drive circuitry employed in heat assisted magnetic recording in high density and high-bit-rate magnetic storage systems in order to ameliorate driver headroom limitations and reduce power consumption.